Hello,
I had the same tensioner. If I understand correctly, the silver protrusion is connected which the cage and is there so that you can make sure the tensioner sprockets are in line with the the wheel sprocket (silimar to the h-l limit screws in a standard derailleur). What I did was unbolt the screw (the pinch bolt), shift the cage to make sure the all the sprockets line up and re-tighten the pinch-bolt. No major forces go through that direction, so hand tight (at leas for me) should be enough for this. I am not sure about the double-sided thing. Hope I helped a bit.
Cheers
edit: Forgot smth, if I remember correctly, the same mechanism, apart from the alignment, controls the amount of tension that the tensioner puts to the chain. With the pinch bolt untight, you can rotate the cage up/down, leading to higher/lower tension respectively.
